Electrolyte membrane with anisotopic swelling and aligned filler

Abstract

An electrolyte membrane ( 11 ) includes: a filler ( 20 ); and a polymer electrolyte ( 22 ). A thickness of the electrolyte membrane ( 11 ) is 1 micrometer to 500 micrometer, a moisture content thereof is 10 mass % or more, and a ratio of a swelling ratio in a membrane surface direction (xy) thereof and a swelling ratio in a membrane thickness direction (z) thereof satisfies following Expression 1: where Lambda z is the swelling ratio in the membrane thickness direction (z), and Lambda xy is the swelling ratio in the membrane surface direction (xy). λ ⁢ ⁢ xy λ ⁢ ⁢ z < 0.3 [ Math . ⁢ 1 ]

The invention claimed is: 
     
       1. An electrolyte membrane, comprising:
 a membrane body comprising: a filler; and a polymer electrolyte, 
 wherein a thickness of the membrane body is 1 micrometer to 500 micrometer, a moisture content of the membrane body is 10 mass % or more, and a swelling anisotropy of a swelling ratio in a membrane surface direction of the membrane body to a swelling ratio in a membrane thickness direction of the membrane body satisfies an equation having the form: 
 
       
         
           
             
               
                 
                   λ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   xy 
                 
                 
                   λ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   z 
                 
               
               < 
               0.3 
             
           
         
         where Lambda z is the swelling ratio in the membrane thickness direction, and Lambda xy is the swelling ratio in the membrane surface direction, and 
         wherein an angle made by a center axis in a longitudinal direction of the filler and a surface parallel to the membrane surface direction is within 45 degrees. 
       
     
     
       2. An electrolyte membrane according to  claim 1 , wherein an aspect ratio of the filler is 10 to 1000. 
     
     
       3. An electrolyte membrane according to  claim 1 , wherein a content of the filler is 1 mass % to 90 mass % with respect to a total mass of the filler and the polymer electrolyte. 
     
     
       4. An electrolyte membrane according to  claim 1 , wherein the filler is oriented in the surface direction of the membrane body. 
     
     
       5. An electrolyte membrane according to  claim 1 , wherein the filler is subjected to surface treatment by an acid. 
     
     
       6. An electrolyte membrane according to  claim 1 , wherein a constituent material of the filler is at least one selected from the group consisting of titania, potassium titanate, silica, silica-alumina, zirconia, and boehmite. 
     
     
       7. A membrane electrode assembly, comprising:
 an electrolyte membrane according to  claim 1 ; 
 an anode catalyst layer and an anode gas diffusion layer, which are arranged on one surface of the electrolyte membrane; and 
 a cathode catalyst layer and a cathode gas diffusion layer, which are arranged on the other surface of the electrolyte membrane. 
 
     
     
       8. A fuel cell, comprising:
 a membrane electrode assembly according to  claim 7 . 
 
     
     
       9. An electrolyte membrane according to  claim 1 , wherein an aspect ratio of the filler is 10 to 500. 
     
     
       10. An electrolyte membrane according to  claim 1 , wherein an aspect ratio of the filler is 10 to 150. 
     
     
       11. An electrolyte membrane according to  claim 1 , wherein the angle is within 30 degrees. 
     
     
       12. An electrolyte membrane according to  claim 1 , wherein an average diameter of the filler is 0.001 micrometer to 10 micrometer.